[1] The phrase Wizard of Oz (originally OZ Paradigm) has come into common usage in the fields of experimental psychology, human factors, ergonomics, linguistics, and usability engineering to describe a testing or iterative design methodology wherein an experimenter (the "wizard"), in a laboratory setting, simulates the behavior of a theoretical intelligent computer application (often by going into another room and intercepting all communications between participant and system).
[citation needed] (His dissertation adviser was the late professor Alphonse Chapatis, sometimes called the "Godfather of Human Factors and Engineering Psychology".)
During the study, in addition to one-way mirrors and other techniques, there was a blackout curtain separating Kelley (the "Wizard") from the participant's view.
The "Experimenter-in-the-Loop" technique had been pioneered at Chapatis' Communications Research Lab at Johns Hopkins as early as 1975 (J. F. Kelley arrived in 1978).
A similar early use of the technique to model a Natural Language Understanding system being developed at the Xerox Palo Alto Research Center was done by Allen Munro and Don Norman around 1975 at the University of California, San Diego.
In that employment the experimenter (the "Wizard") sat at a terminal in an adjacent room separated by a one-way mirror so the subject could be observed.
"Offline Zero" was a reference to the fact that an experimenter (the "Wizard") was interpreting the users' inputs in real time during the simulation phase.
It sometimes lacks the real computer's speed and accuracy, but a team of experts working simultaneously can compensate to a sufficient degree to provide an acceptable simulation.
The processing model was a two-pass keyword/key-phrase matching approach, based loosely on the algorithms employed in Weizenbaum's famous Eliza program.
In the early development sessions, the experimenter simulated the system in toto, performing all the database queries and composing all the responses to the participants by hand.
In the 23 years that followed initial publication, the OZ method has been employed in a wide variety of settings, notably in the prototyping and usability testing of proposed user interface designs in advance of having actual application software in place.